Becarre, Bemol

Sauter de bécarre en bémol (French), to jump from one subject
to another without regard to pertinence; “Sauter du coq à l'ane,”
from Genesis to Revelation. Literally, to jump from sharps to flats.
Becarre is the Latin B quadratum or B quarré. In old
musical notation B sharp was expressed by a square B, and B flat by a
round B.